This invention relates to liquid filters and particularly to filters which are capable of separating gases and liquids and of venting the gases. The invention specifically relates to filters of the character described which are capable of separating gas from liquid in fluids which are administered to a living patient.
The entrainment of gases in liquids and of liquids in gases are common problems which require apparatus to separate the gas from the liquid. This is particularly true in filters used for filtering blood, plasma, parenteral solution, or other fluid to a living patient, usually human. In addition to filtering out particulate matter and potentially harmful micro-organisms, it is extremely important that no entrained gas remain in the fluid so as to eliminate any hazard of embolism from air or gas reaching the patient. However, there are various continuing problems in using such filters in the medical field.
One problem involves the cost of such filters which, itself, is a continuing nemesis of the medical industry. It is desirable to provide relatively inexpensive instruments, such as syringes, or the like, which are sufficiently inexpensive to manufacture that they are disposable after use with an individual patient. This avoids costly manpower and equipment to continuously clean and re-use the medical equipment. This is equally applicable for intravenous filters, for instance. Heretofore, gas separating and venting filters have incorporated hydrophilic and hydrophobic subassemblies which greatly increase the cost of such filters.
Another problem concerns the use of such filters on a patient so that the filters are completely operative in any position or orientation. For instance, it is desirable to utilize the filters in-line with the flow of fluid and which may be directly or indirectly attached to a movable body member of a patient. Movement of the patient effects different orientations of the filter and the filter must be operative in any position. Without such capabilities, gas bubbles accumulate within the filter, touching the hydrophilic filter element and thereby inhibiting the flow of liquid therethrough.
A further problem concerns the build-up of pressure in the system and on the fluid flowing through the filter to a patient. This can harm the patient. Heretofore, pressure build-ups have been compensated for by mechanisms extraneous of the filter to avoid excessive pressures on the fluid, either before or after the fluid passes through the filter. It would be highly desirable to provide an automatic pressure compensating means directly in the filter, particularly without increasing the cost or size of the filter itself.
The present invention is directed to providing a new and improved filter of the character described which is directed to solving these varying problems in a very simple and inexpensive gas separating and venting filter.